The invention described herein is generally related to magnetic compasses. More particularly, this invention is related to remotely readable magnetic compasses.
In various applications there is a need for a directional compass which can be read from a remote location. For example, in the operation of remotely controlled submersible marine vehicles it is desirable to monitor the geographic orientation of the vehicle by means of a remotely readable compass located onboard the vehicle. Similarly, in oil and gas field well logging operations it is sometimes necessary to monitor the geographic orientation of a tool or down-hole instrumentation package. Remotely readable compasses are also useful in towed undersea hydrophone arrays used in marine geophysical research, in sonobuoys used in naval operations, and in remotely controlled airborne meteorological instruments.
Although it is considered to be a straightforward matter to design a remotely readable compass using various well-known electronic transducers and the like, there is a need in some applications for simpler yet more reliable assemblies. For example, there is a need in some applications, particularly in the undersea applications noted above, for a remotely readable compass which does not require a battery or other independent power supply, and which is free of other electronic components so as to be relatively immune to the effects of corrosion and electromagnetic interference.
Further, remotely controlled instrumentation packages are increasingly being connected to remote stations by means of optical fibers, which are light in weight, inexpensive, and less susceptible to the effects of salt water or electrical interference. As optical fibers become increasingly prevalent in instrumentation packages, it becomes increasingly desirable to eliminate electrical wires and cables altogether, so that communication can be simplified by the use of single multi-strand optical fiber cables.